HISTORY OF GALVANISM. 5 



portions requisite to form water. Mr. Davy then wimed to Reverfe effect 



afcertain whether' it was eflential for the wires to be in contaft on afin g le . inter * 



mediate wire. 

 with the metallic plates of the pile; the ends of the pile were 



therefore made to communicate with two glades of water by 



pieces of mufcular fibre, and the glafles were connected by a 



filver wire. The effects of the pile were now reverfed. Hi- 



drogen was difengaged by the wire at the zinc end, while the 



wire at the filver end became oxidated. 



Col. Haldane, in a fecond memoir, details a feries of experi- Col. Haldanc 



ments made to determine the power of different combinations . sws J hat the 



r pile acts more 



of metals. He found the pile acted more powerfully when mi- ftrongly in ox- 



merfed in a given quantity pfoxieen gas, than when confined in 'S^* and not at 

 , r , n ,- r i • i -. i- Z- i r r all in azote or m 



the lame bulk of atmolpherical air; its action was entirely iul- vacuo. 



peuded in azote or in a vacuum. On this account he conjec- 

 tures that the effects of galvanifm djepend upon a chemical 

 operation, and that oxigen is attracted by the apparatus from 

 the atmofphere. 



Mr. Davy difcovered that the influence of the pile was Davy's applica- 

 capable of being tranfraitted through charcoal, when an appa- t]on ^ cb f'^ al 

 ratus was conftrucled of this fubflance and filver. It decom- 

 pofed water in the ufual manner, the filver end giving out hi- 

 drogen with a little carbon in folution, while the zinc end evol- 

 ved but little gas of any kind ; this was probably owing to the 

 abforption of the carbonic acid which would be formed at this 

 end of the wire. He found '^at when the water between, the His difcoveries 

 pairs of metallic plates was perfectly pure, i. e. when it ^ jn^aualTn 

 contained neither acid, fait, nor gas of any kind, the pile the pile, and th?t 



ceafed to acl. He conjectures that the energy of the pile is lts efte ^ s a y e 



J * % . f> y * proportioned to 



nearly in proportion to the rapidity with which the zinc be- the oxidation. 



.comes oxidated ; and confequently the effects were found to 

 be the moil powerful when nitric acid was interpofed between 

 the metals. Mr. Davy appears in this inftance to have made He applies the 

 the hrft ftep towards the true theory of the action of Volta's acids » 

 pile : as might be inferred from this notion, he found that con- 

 centrated fulphuric acid interpofed between the metals, acted 

 Jefs powerfully than diluted fulphuric acid, becaufe this laft has 

 more power in oxidating zinc than when in its pure ftate. He and caufes the 



alfo difcovered that the pile can act in vacuo, provided a little P heto aft m 



1 * vacuo, 



acid be interpofed between the plates. A pile compofed of 



zinc and charcoal was found to poflefs gr<eat energy. 



All 



